Treatment of iron ores containing nickel



Jan. 12, 1937. E. H. BROWN ET AL 2,067,374

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UNITED STATES PATENT OFFICE TREATIWENT-OF IRON ORES CONTAINING NICKEL Earl H. Brown and Sylvester James Broderick, Yellow Springs, Ohio, assignors to Bethlehem Mines Corporation, a corporation of Delaware Application August 29, 1932, Serial No. 630,907- 11 Claims. (01. 75-111) This invention relates to the treatment of ed by low temperature reduction, it has been complex iron ores, which contain nickel as an customary to submit the mass discharged from intimately associated minor constituent, in the the reduction furnace to magnetic separation or form of oxide or silicate. Such ores, when to operations well known in ore dressing. In smelted in ablast furnace, result inthe complete the'present case, the presence of partially rereduction of the nickel with the iron and its duced iron ore makes aclean separation of a consequent inclusion in the pig iron, as an almetallized portion diflicult. loying component. The presence of nickel is not Another method is to heat the mass to fusion 1 required in ordinary commercial grades of steel and effect a separation of metal from gangue and it is therefore desirable to. eifect its reor slag by liquation. With the larger pro- 10 moval to a substantial degree,'prior to charging portion of the iron oxide unreduced, such a the ore to the blast furnace. method is clearly impracticable in the present The present invention is directed to the concase. On the other hand if the initial reducversion of reduced or metallized nickel, derived tion were carried out under conditions that from the ore, to a soluble form such as nickel would insure reduction of a major portion of chloride, without involving any serious loss of the the iron as well as the nickel, the result of fusion iron, with which it is. associated. The method would be to alloy the nickel and iron, a result to be disclosed, provides for the removal of all it is specifically desired to avoid. but a trace of nickel with a, loss in iron of only An important feature of this invention is there- 5% or less. fore the removal, by chemical treatment, of the The drawing shows a flow sheet of the procmetallized portion of the ore from that unreess disclosed in this application. duced; and it has been found that chlorination In order to render the nickel in its mineralogto render soluble the metallized portion offers ical form, susceptible to chlorination, it must an efiective method of removal. Any of the first be reduced to a metallic condition. To known chlorinating agents may be used, but avoid a complete reduction of the ore, such as chlorine gas, because of its comparative ease of would obtain under ordinary smelting condicontrol, is the preferred medium. tions, the desired result may be best obtained When using chlorine a temperature of about by reduction at low temperatures, that is to say, 200 C. has been found to give satisfactory rebelow the fusion point of the ore. As already S- A higher temperatures e kel 30 known the low temperature reduction of Mayari tractable by water leaching is decreased, and ore, may result in the reduction of all the nickel the soluble iron tends to increase; whereas at and the greater part of the iron, the chromium room temperature the results do not greatly vary remaining unreduced. from those obtained at 200 C. The time re- Various methods of low temperature reducquired for chlorination depends somewhat on the 35 tion have been contemplated for this ore and it physical condition of the ore after its initial rehas been found that hydrogen or a hydrogen duction, the average particle size of the product containing gas is particularly effective and perand the quantity under treatment for any premits of the desired degree of reduction at subdetermined flow of gas. At 200 C. for any specistantially low temperature. Carbon monoxide fied condition of the ore, there is an optimum 40 which is also an efllcient reducing agent retime for best extraction of nickel and least loss quires a somewhat wider range of temperature of iron, the exact determination of which is best for reduction. However when using hydrogen determined experimentally in the actual appaas the reducing agent at temperatures rangratus for chlorination. However comparing the ing from 600 C. to 700 C.acomparatively quick time taken for reduction at 600 C. and that 45 reduction of nickel is eifected, while the 'iron for chlorination at 200 C., it may be said that is only reduced in part. For example at 600 C. the first named gives best results with a com- 91.8% of the nickel may be reduced, but only paratively short exposure to the reducing gas, 13.4% of the iron. As the temperature is inwhereas chlorination proceeds more slowly. Uncreased the proportion of iron that is reduced is der the conditions ruling in various experimental also substantially greater and, for the purpose runs, it has been found that the time for chloriin view, it is desirable to keep the reduced iron nation may well be extended to periods four as low as, practicable. times the duration of the reduction phase.

In order to separate the reduced from the For the removal of the soluble nickel'chloride unreduced portion of an ore that has been treatany of the known methods of leaching with wa- 55 ter, continuous counter current decantation for taken of the decreased solubility of ferric chloride in hot water at about 85 C. or just below the boiling point as compared with its solubility at normal temperature; the solubility of the nickel chloride remaining practically unaffected. In this manner substantially the whole of the soluble nickel may be leached from the mass and about half of the soluble iron. The residue therefore contains only .a very small proportion of the original nickel (less than 10%), together with 80% or more of the original iron as oxide and a small proportion of unleached ferric chloride; under optimum conditions the iron loss in the leach solution may be limited to about 5%. This residue after drying and agglomeration by sintering is suitable for smelting in a blast furnace and will result in a pig iron, in which the nickel content has been reduced to a trace.

Moreover, by following the above methods of reduction without fusion, followed by chlorina tion, an alternative method of removing chlorinated nickel with minimum removal of iron may be used. It has been found that by raising the temperature 0. the chlorinated mass, after chlorination has been effected to the desired degree, to about 300 C., an effective separation of the ferric chloride from the nickel chloride by sublimation of the former may be attained. To prevent any reversal of the chlorine reaction at the higher temperature, it has been found advantageous to maintain the flow of chlorine during the period of sublimation. As indicated in a previous paragraph, presence of chlorine at a temperature above 200 C. tends to increase the amount of iron chloridized, however at 300 C. the greater part of the ferric chloride formed sublimes and may be recovered in or near the gas outlet of the apparatus, or in suitable condensing means provided therefor. In this manner the actual loss of iron in leaching may be decreased to 2% or less of the original iron in the untreated ore and practically all the nickel may be removed.

From the above it can be seen that nickel may be effectively removed from an iron ore, in which it exists as an impurity by the combination of preferential reduction, preferential conversion to soluble form and preferential removal from the zone of conversion. While the process steps have been principally directed to a specific case of a nickeliferous iron ore, it will be evident to one skilled in the art, that the several steps disclosed are individually susceptible to adjustment in respect to temperature and time of treatment according to the condition of the ore and the proportion of nickel it contains.

The specific features of the invention are set forth in the following claims.

We claim:

1. A process for the treatment of nickeliferous iron ores, which consists in effecting a selective low temperature reduction of the ore under conditions favoring complete reduction of the nickel without substantial reduction of the iron, chlorinating the reduced nickel and iron at a temperature favorable to a complete conversion of the reduced nickel to soluble chloride and some conversion of the reduced iron to chloride, and leaching the product of chlorination with hot water at a temperature at which the solubility of iron chloride is a minimum but the high solubility of nickel chloride is unaffected.

2. A process for the treatment of nickeliferous iron ores, which consists in eil'ecting a selective low temperature reduction of the ore under conditions favoring complete reduction of the nickel without substantial reduction of the iron, chlorinating the reduced nickel and iron at a temperature not exceeding about 200 C., and leaching the product of chlorination with water at a temperature slightly below its boiling point, to preferentially romove nickel chloride from the mass.

3. A process for the treatment of nickeliferous iron ores, which consists in, eifecting a selective low temperature reduction of the ore to metallic nickel at a temperature below 800 C. by means of a reducing gas, chlorinating the metallized product of reduction at a temperature not exceeding about 200 C. and leaching the chlorinated mass so as to remove the soluble chlorides.

4. A-process for the treatment of nickeliferous iron ores, which consists in, reducing the ore to metallic nickel with gas containing hydrogen at a temperature below 800 C., chlorinating the metallized product of reduction at a temperature not exceeding about 200 C. and leaching the chlorinated mass so as to remove the soluble chlorides.

5. A process for the treatment of nickeliferous iron ores, which consists in, reducing the ore to metallic nickel with hydrogen gas at about 600 C., chlorinatingthe metallized product of reduction at a temperature not exceeding about 200 C. and leaching the chlorinated mass so as to remove the soluble chlorides.

6. A process for the treatment of nickeliferous iron ores, which consists in, submitting the ore to low temperature reduction under conditions to metallize all the nickel and only a minor portion of the iron, chlorinating the reduced nickel and iron at substantially low roasting temperature, and raising the temperature of the roast after full chlorination of the nickel has been effected, so as to volatilize and sublimate the iron chloride, said increase in temperature being applied while maintaining a flow of chlorinating gas over the mass, and after sublimation of the iron chloride, removing the soluble nickel chloride by leaching.

7. A process for the treatment of nickeliferous iron ores, which consists in, submitting the ore to low temperature reduction under conditions to metallize all the nickel and only a minor portion of the iron, chlorinating the reduced nickel and iron at a temperature not exceeding 200 C. until substantially complete conversion of the nickel to nickel chloride has been eflected. raising the temperature to about 300 C. while maintaining a flow of chlorine over the roast, until the iron chloride has been volatilized and sublimated to a substantial degree, and. leaching the roast to remove the soluble nickel chloride.

8. A process for the treatment of nickeliferous iron ores, which consists in, selectively reducing to metal the nickel and a minor part of the iron at a temperature substantially below the fusion point of the ore, selectively chloridizing the reduced nickel to a soluble salt, and removing by leaching the nickel chloride and any incidental ferric chloride formed.

9. A process for the treatment of nickeliferous iron ores, which consists in, selectively reducing to metal the nickel and a minor part of the iron at a temperature substantially below the fusion point of the ore, selectively chloridizing the reduced' nickel to a soluble salt, subliming any incidental ferric chloride formed, and removing the nickel chloride by leaching.

10. A process for removing nickel irom'a nick- 'eiiierous iron ore which consists in deoxidizing the nickel ore to finely divided sponge nickel containing metallic iron as an impurity, cooling the sponge to normal temperature, converting the sponge nickelto nickel chloride and the metallic iron to ferric chloride by. treatment with chlorine gas at temperature not exceeding about 200 0., and leaching the chlorinated mass at about 80 C. to remove the nickel chloride preferentially to the ferric chloride in said mass.

ILA process for removing nickel irom a nickeliierous iron ore which consists in deoxidizing taining metallic iron as an impurity, cooling the sponge to normal temperature, converting the sponge nickel to nickel chloride and the metallic iron to ferric chloride by treatment with chlorine gas at temperature not exceeding about 200 C., raising the temperature to about 300 C. to volatilize the ferric chloride and leaching the nickel chloride from the residual ore.

EARL H. BROWN.

8. JAMES BRODERICK.

- the nickel ore to ilnely divided sponge nickel con- 

